Application Notes
1.0 BENEFITS OF THE LMV321/358/324
Size: The small footprints of the LMV321/358/324 packages
save space on printed circuit boards, and enable the design
of smaller electronic products, such as cellular phones, pag-
ers, or other portable systems. The low profile of the
LMV321/358/324 make them possible to use in PCMCIA
type III cards.
Signal Integrity
Signals can pick up noise between the signal source and the
amplifier. By using a physically smaller amplifier package,
the LMV321/358/324 can be placed closer to the signal
source, reducing noise pickup and increasing signal integrity.
Time (50µs/div)
10006097
Simplified Board Layout
These products help you to avoid using long pc traces in
your pc board layout. This means that no additional compo-
nents, such as capacitors and resistors, are needed to filter
out the unwanted signals due to the interference between
the long pc traces.
FIGURE 1. Output Swing of LMV324
Low Supply Current
These devices will help you to maximize battery life. They
are ideal for battery powered systems.
Low Supply Voltage
National provides guaranteed performance at 2.7V and 5V.
These guarantees ensure operation throughout the battery
lifetime.
Rail-to-Rail Output
Rail-to-rail output swing provides maximum possible dy-
namic range at the output. This is particularly important
when operating on low supply voltages.
Time (50µs/div)
10006098
FIGURE 2. Output Swing of LM324
2.0 CAPACITIVE LOAD TOLERANCE
Input Includes Ground
Allows direct sensing near GND in single supply operation.
The differential input voltage may be larger than V+ without
damaging the device. Protection should be provided to pre-
vent the input voltages from going negative more than −0.3V
(at 25˚C). An input clamp diode with a resistor to the IC input
terminal can be used.
The LMV321/358/324 can directly drive 200pF in unity-gain
without oscillation. The unity-gain follower is the most sensi-
tive configuration to capacitive loading. Direct capacitive
loading reduces the phase margin of amplifiers. The combi-
nation of the amplifier’s output impedance and the capacitive
load induces phase lag. This results in either an under-
damped pulse response or oscillation. To drive a heavier
capacitive load, circuit in Figure 3 can be used.
Ease Of Use & Crossover Distortion
The LMV321/358/324 offer specifications similar to the fa-
miliar LM324. In addition, the new LMV321/358/324 effec-
tively eliminate the output crossover distortion. The scope
photos in Figure 1 and Figure 2 compare the output swing of
the LMV324 and the LM324 in a voltage follower configura-
tion, with V S
=
2.5V and RL (= 2kΩ) connected to GND. It
is apparent that the crossover distortion has been eliminated
in the new LMV324.
10006004
FIGURE 3. Indirectly Driving A Capacitive Load Using
Resistive Isolation
13
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